#include <stdio.h>
#include <sys/eventfd.h>
#include <unistd.h>

int main(){
    int fd = eventfd(1234, 0);
    uint64_t one;
    read(fd, &one, sizeof(one));
    printf("%lu\n", one);
    //read(fd, &one, sizeof(one));
    //printf("%lu\n", one);
    //one = 12;
    //write(fd, &one, sizeof(one));
    one = 20;
    write(fd, &one, sizeof(one));
    read(fd, &one, sizeof(one));
    printf("%lu\n", one);

    
}